In, for example, phosphoric acid fuel cells the electrodes can be damaged if the electrical potentials exceed certain limits. For example, the cathode of the fuel cell will undergo catalyst dissolution, catalyst support dissolution and catalyst layer flooding, if the potential exceeds, for example, eight-tenths (0.8) of a volt. In the other extreme, if it approaches the anode potential and is subsequently re-oxidized, re-crystallization of the catalyst takes place, and activity is lost. If the anode is allowed to approach the cathode potential [approximately, e.g., eight-tenths (0.8) of a volt], it will flood with electrolyte.
Electrical potential control for the fuel cell is most necessary during off-power conditions or non-operating modes, for example, during power plant shutdown, start-up and hot holds.
The present invention is directed generally to enhancing fuel cell electrical potential control, particularly during adverse conditions, and more particularly to the means used to add one component of the reactant gas to the other(s).